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For Modbus RTU/ASCii, we can simulate as many as 5 servers ( we call it 5 devices too).
The 1st device to 4th device have the same registers structure, and the same watchdog.
The 5th device has different registers structure, different watchdog.
We call one consecutive Modbus register addresses "Segment". For one kind of registers, we can have maximum 10 segments.
For example, we can have maximum of 10 holding registers segments, maximum of 10 input registers segments, maximum of 10 coils registers segments, maximum of 10 discrete registers segments.
We use hardware to implement all registers, so it has hardware resource limit. All devices' word registers Quantities cannot be over 720, All devices' bit registers Quantities cannot be over 1024.
We have built-in hardware watchdog, There are 2 different hardware watchdog, one is using Read-only word register. The other is using Read-write word register. Server can only supports one kind of watchdog. It cannot support 2 kinds of watchdog at the same time.
For Read-only word register watchdog, it is for master node to identity Modbus communication normal or fault. It has 2 watchdog types, type 0 for increasing 1 every Watchdog periods, type 1 for decreasing 1 every Watchdog periods. The outside master can read this Watchdog register value to know whether slave node is OK.
For Read-write word register watchdog, it is for slave node itself to identity Modbus communication normal or fault. Outside Master must write this watchdog register periodically. It has 3 watchdog types, type 0 for un-changed watchdog value which means value is decided by outside master, type 1 for increasing 1 every Watchdog periods until it equals Preset value, type 2 for decreasing 1 every Watchdog periods from Preset value until it equals 0. So Outside master must write watchdog value periodically, otherwise for any type of watchdog, slave node can easily know abnormal fault state. Customer's VBScript or Matlab script or Simulink block will do judgment of Modbus communication status.
Please firstly use PC_Utility Software under Microsoft windows platform to set up Bus configuration including Modbus type, Baud rate, Hardware interface (RS485/RS422/RS232) if you first time use hardware of simulator.
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